1. Field of the Invention
The present invention relates to apparatus for carrying out harmonic oscillation analysis and more particularly relates to such apparatus for determining the cause for abnormal vibration occurring in a machine system whose operation is accompanied by vibration, by extracting the harmonic oscillation.
2. Description of the Prior Art
It is well-known that in machines such as rotary machine systems there are often generated during its rotation various vibrations in axial, radial and rotational directions which bring the rotary system into an undesirable abnormal state. To detect such abnormal vibration, hitherto, many abnormality watching and/or forecasting methods have been employed. According to one of the known methods, acceleration, velocity and displacement of vibration are detected by using a detector to electrically obtain the wave form of the vibration. Based on the obtained wave form, discrimination of frequency and/or amplitude of the occurring vibration is conducted. According to another known method, signal level in a specific frequency band is detected.
However, these abnornal vibration watching and forecasting methods according to the prior art are generally unsuitable for analyzing the cause for abnormality precisely and in detail. Since according to the prior art methods oscillation wave forms in relatively broad frequency band are processed, it is difficult to determine the details of the cause for abnormal vibration occurring in a rotary machine system.